[llvm] [SLP] Avoid crash in computeExtractCost (PR #93188)

[Björn Pettersson via llvm-commits]

bjope wrote:

The problem attempted to be solved here was solved by commit 70a54bca6f7f9f45b4b17974d (https://github.com/llvm/llvm-project/pull/93213) instead.

https://github.com/llvm/llvm-project/pull/93188